The present invention is directed to error-correction-code generation. It is directed particularly to the sequencing of words within a block of data to be encoded in accordance with a complex encoding scheme.
A relatively recent development in the art of phonograph recordings is the so-called compact disc, which stores audio information in digital form. Because of the high density and low cost of this storage medium, the compact disc has been proposed for storing other kinds of data, too. But storage of, say, financial data requires more accuracy than storage of audio information does. The misreading of an occasional bit during playback of audio data is very tolerable; it ordinarily is not even noticed. The same cannot be said of financial data. Thus, in adapting the compact disc to other types of data storage, a greater degree of error-correction coding must be added.
Error-correction-code words typically are generated in operations performed on groups of data words. In one proposed code-generation scheme, these groups are assembled, not from consecutive data words, but from words selected in complex sequences. Because of the complex sequencing, the data handling required in the encoding operation is quite complicated. Even in dedicated circuitry, calculation in real time of the addresses from which successive words must be fetched for processing can push the limits of circuit speed, and the address-calculation circuitry can contribute significantly to the complexity of the total encoding circuit.
It is accordingly an object of the present invention to process the data at the rates at which it ordinarily is received and to employ a minimal amount of hardware to do so.